The present invention relates to sanitary absorbent articles such as sanitary napkins, pantiliners and adult incontinence pads. More specifically, it relates to the construction of the body faceable cover layer of such articles.
Sanitary absorbent articles are articles of manufacture that generally are used to absorb and retain bodily exudates; they have both medical and non-medical uses. Conventional sanitary absorbent articles generally comprise several different layers of material joined together to form a laminate. Each of these layers is referred to as a xe2x80x9ccomponent layerxe2x80x9d and serves a specific function within the article. Each layer is thus usually fabricated from a material different than that of the others, and has different physical properties and characteristics.
The uppermost layer of material, i.e. the layer that is intended to face the body of a wearer of the article when the article is in use is conventionally termed the xe2x80x9ccover layerxe2x80x9d or xe2x80x9ctop sheetxe2x80x9d. The cover layer is generally relatively soft to the touch so as to avoid discomfort and prevent abrasions to the human tissue with which it is in contact during the time which the article is worn. The cover layer is fluid permeable to permit the ingress of bodily exudate into the article to be absorbed and retained. At the same time, however, the cover layer preferably remains dry to prevent moisture from accumulating against the skin of the wearer causing irritation. In order to meet these desired characteristics, conventional cover layers are manufactured from non-woven fibrous materials or polymeric, preferably thermoplastic, films, having a large number of relatively small apertures per unit surface area. Each of these types of materials is well known in the art.
Neither of these materials is, however, without its drawbacks. Non-woven fibrous materials have the characteristic of planar (lateral) wicking. As described above, it is generally desired that bodily exudate to be absorbed by the article pass through the cover layer to the absorbent layer therebelow. As non-woven cover layers comprise fibrous components, however, some bodily exudate will wick in the plane of a cover layer owing to the capillary action of the fibers thereof. Depending on the quantity of exudate impinging upon the cover layer, such bodily exudate will eventually migrate to the sides of the article and will egress the cover layer and soil the garments (or undergarments) of the wearer. In many non-woven cover materials the fibers are generally oriented all in the same direction, usually either parallel to the longitudinal centerline or to the transverse centerline of the article (these axes are well known to those skilled in art and are also defined below). In these covers the majority of lateral wicking occurs in a direction parallel to that of the fiber direction. As the length of the article in a direction parallel to the transverse centerline is shorter than that in a direction parallel to the longitudinal centerline, this problem is therefore much worse when the fibers are oriented parallel to the transverse centerline, particularly in a central region of the article.
In contrast, apertured thermoplastic films do not gene rally wick fluids within the plane of the film, as they do not comprise fibrous elements, nor are they intrinsically absorbent. Thus, substantially no lateral wicking occurs and substantially the entirety of exudate impinging upon cover layers of these materials passes therethrough to the absorbent layer below. The disadvantage of such materials is that they may feel hot and sticky against the skin of a wearer, and may be thus uncomfortable. In addition, the absorbent core directly below the source of body exudate has a greater tendency to become saturated.
One solution to the potential problem of the hot and sticky feel of the apertured thermoplastic film is a sanitary absorbent article having a composite cover layer as described in International Patent Application Publication No. WO 93/09744. The composite cover layer described therein has a central zone extending longitudinally down the center of the article, and end zones extending laterally (transversely) from the central zone. The central zone comprises an apertured thermoplastic film, while the end zones comprise a non-woven material. The stated purpose of such a construction is to position the non-woven material in areas likely to come into contact with the skin of the wearer, while still retaining some of the benefit of having an apertured thermoplastic portion of the cover layer.
A cover layer of such construction suffers from two distinct problems. The first is that the regions of the cover layer which are near the transverse ends of the article also come into contact with the skin of the wearer, yet they still comprise a thermoplastic film. Thus, these portions may still feel hot and sticky to a wearer of the article. The second problem with such a construction is that the end zones (as described therein) still comprise a non-woven material in their marginal portions, thus any body exudate coming into contact therewith risks being wicked to the longitudinal edge of the article and staining the undergarments of the wearer. Moreover, it has been observed that generally, wearers of such articles would prefer to suffer a minor inconvenience in the form a slight hot and sticky feel rather than have the article fail to retain all of the body exudate impinging on it, and having their garments/undergarments soiled by such exudate.
There is therefore still a need in the art to provide a sanitary article having an improved cover layer construction. There is particularly a need to provide a sanitary absorbent article having reduced incidence of side leakage owing to lateral wicking along the cover layer, while reducing the hot and sticky feel associated with prior art articles having cover layers comprising apertured thermoplastic films.
It is thus an object of the present invention to pro vide a sanitary absorbent article having an improved cover layer construction.
It is another object of the present invention to provide a sanitary absorbent article having reduced incidence of side leakage owing to lateral wicking along the cover layer, while reducing, to some extent, the hot and sticky feel associated with prior art articles having cover layers comprising apertured thermoplastic films.
In accordance with the present invention, there has been provided a sanitary absorbent article adapted to be worn in a crotch portion of wearer""s undergarment having a main body portion with two opposing longitudinal sides, two opposing transverse sides, an imaginary longitudinal centerline and an imaginary transverse centerline; the main body comprising:
(A) a fluid-pervious cover layer, the cover layer facing towards a wearer""s body when the article is in use by a wearer;
(B) a fluid-impervious barrier layer, the barrier layer facing away from the wearer""s body when the article is in use by the wearer;
(C) an absorbent system intermediate the cover layer and the barrier layer; the cover layer having:
(1) an intermediate zone located in a centrial region of the main body and adapted for registration with a source of bodily exudate to be absorbed by the article when the article is in use by the wearer, the intermediate zone including marginal portions adjacent the respective longitudinal sides of the main body and extending towards the longitudinal centerline, the marginal portions comprising a material having a higher degree of vertical liquid migration than lateral liquid migration; and
(2) a first terminal zone adjoining the intermediate zone and extending longitudinally away therefrom toward one of the transverse sides of the main body, the first terminal zone comprising a material having a higher degree of lateral liquid migration than vertical liquid migration.
The sanitary napkin of the present invention may optionally be provided with flexible flaps that project laterally outward from the longitudinal sides of the main body and which are adapted to be folded about the edges of the crotch portion of the undergarment. The longitudinal sides of the main body defines the interface or common boundary between the flaps and the main body and is not considered to form part of the flaps. Thus, with respect to embodiments of the present invention that do not possess flaps, the longitudinal sides of the main body also define the outer edges of the sanitary napkin.
In a specific nonlimiting example of implementation, each marginal portion has a minimum transverse dimension of not less than about 1.5 cm. The term xe2x80x9cminimum transverse dimensionxe2x80x9d refers to a specific dimension of each marginal portion determinable as follows. A reference point on the sample of the sanitary absorbent article that is disposed beneath the source of bodily exudate, when worn, is located. A plane parallel to the transverse centerline and 2.0 centimeters forward from the reference point (a direction along the longitudinal centerline of the sanitary absorbent article) is located. Another plane parallel to the transverse centerline and 2.0 cm rearward from the reference point (a direction along the longitudinal centerline of the sanitary absorbent article) is also located. The smallest width of the marginal portion (the dimension measured along the transverse centerline of the sanitary absorbent article) occurring at any point between the two parallel planes defined above constitutes the xe2x80x9cminimum transverse dimensionxe2x80x9d of the marginal portion. In a preferred embodiment, the minimum transverse dimension of each marginal portion is at least 2.0 cm.
Preferably, the cover layer further includes a second terminal zone adjoining the intermediate zone and extending longitudinally away therefrom toward the other of the transverse sides of the main body, the second terminal zone comprising a material having a higher degree of lateral liquid migration of bodily exudate than vertical liquid migration of bodily exudate.
It is preferred that the main body of the article be generally rectangular with rounded ends. When the article is of such a conformation, the first and second transverse sides are the shorter opposing sides and will generally have an arcuate shape. The first and second longitudinal sides are the longer opposing sides and may be substantially straight or arcuate, and are preferably inwardly arcuate to form a generally hour-glass or dog-bone shape.
The longitudinal centerline of the article is an imaginary line that extends longitudinally between the opposite transverse sides along an intermediate portion of the article which is substantially equidistant from the longitudinal sides thereof. It will thus bisect the article into two generally mirror image halves. As these articles are worn in the pudendal region, when the article is in use by a wearer, the longitudinal centerline thereof is generally parallel to, or most commonly, lies in, the sagital plane of the wearer. The transverse centerline is an imaginary line that extends transversely across the article, and is typically, but not always, equidistant from the transverse sides thereof. The transverse centerline is thus perpendicular to the longitudinal centerline. Where the article has flaps, the transverse centerline is generally the line perpendicular to the longitudinal centerline that bisects the flaps.
The article is of a laminate construction and in most cases will have at least three layers. The first of these layers is the cover layer. The cover layer has two major surfaces, the first is an external surface (i.e. a surface that does not face another component layer of the article), which, when the article is in use by a wearer, faces the wearer""s body. The other surface is an internal surface (i.e. a surface that faces another component layer of the article), which faces the absorbent system below.
The cover layer is fluid-permeable, and thus will permit the body exudate to be absorbed by the article to pass through it into the layers below. The cover layer has an intermediate zone and two terminal zones. The intermediate zone is generally the zone of the article, which, when the article is correctly positioned with respect to the body of al wearer, is the initial contact point of the majority of the exudate to be absorbed by the article. Thus, when the article is a sanitary napkin, for example, the intermediate zone of the article will be located substantially in a central region of the article and is adapted to register with the vaginal opening of the wearer (the source of the exudate). The intermediate zone preferably has a longitudinal length, as measured along the longitudinal centerline of the article, of between about 2.5 and 12.5 cm and most preferably 7.5 cm.
In order to prevent bodily exudate to laterally wick across (in the plane of) the cover layer, the marginal portions thereof are constructed from a material that has a higher degree of vertical liquid migration than lateral liquid migration. The material of choice is selected such that when bodily exudate is deposited on the cover layer substantially no lateral liquid migration occurs (hereinafter this material is referred to as the xe2x80x9cnon-lateral liquid migration materialxe2x80x9d for ease of reference). Preferably this material is an apertured polymeric film, preferably apertured thermoplastic film having a three dimensional character. In the context of the present specification, the term xe2x80x9cmarginal portionsxe2x80x9d is used to indicate the regions of the intermediate zone of the cover layer adjacent the longitudinal sides of the main body and preferably starting at the longitudinal sides of the main body and extending inward towards the longitudinal centerline of the article. Preferably, the marginal portions comprising the non-lateral liquid migration material each comprise at least 15% of surface area of the total surface area of the intermediate zone. More preferably, they each comprise at least 20% of the total, still more preferably at least 25% of the total.
In accordance with one embodiment of the invention, the entire intermediate zone is a compound structure including a combination of a non-lateral liquid migration material and some other liquid pervious material wherein the marginal portions are constructed of the non-lateral liquid migration material to provide a barrier to lateral wicking. In accordance with this embodiment, the central area of the intermediate zone includes a non-woven fabric zone while the marginal portions of the intermediate zone are made of apertured film. In this form of construction, lateral liquid migration will occur in the non-woven fabric zone, but not in the marginal portions of the intermediate zone.
In order to increase the efficiency of the barrier (liquid migration resistance) effect of cover layers of this construction, it is preferred that the boundary between the two materials forming the intermediate zone lie interior (i.e. closer to the longitudinal centerline) than the edge of the absorbent system. In a specific example of implementation the distance (measured along the transverse centerline) separating the two boundaries is of about 5.0 cm while the width of the absorbent system is of about 6.6 cm.
In a most preferred embodiment of the invention, the entire intermediate zone is constructed of the non-lateral liquid migration material. In such a case, the non-lateral liquid migration material is still preferably an apertured thermoplastic film.
The terminal zones of the cover layer extend longitudinally from the intermediate zone to the transverse sides of the article. By xe2x80x9clongitudinallyxe2x80x9d it is meant that the terminal zones extend in a direction generally parallel to the longitudinal centerline of the article. The terminal zones are in a large majority, and preferably in their entirety, constructed of a fibrous material, preferably a non-woven fibrous material, to be comfortable to the wearer of the article. The terminal zones do not need to be constructed from the same material.
The interface between portions of the cover layer being constructed of a non-lateral liquid migration material and portions constructed of a non-woven fibrous materials may take a variety of forms. It is most preferred that the portions constructed of non-lateral liquid migration material overlap those portions constructed of non-woven fibrous materials. In this manner, the non-woven fibrous material will laterally wick exudate underneath the non-lateral liquid migration materials, toward the absorbent system below.
The overlapping portions are sealed together by one of a variety of conventional means, e.g. by means of adhesives, heat-bonding, ultrasonic bonding, radio frequency sealing, mechanical crimping, and the like and combinations thereof. Adhesive sealing is preferred. To the greatest extent possible, the sealing method should leave a smooth surface on the body faceable surface of the cover layer so as avoid formation of irregularities that can irritate the user of the article.
It should be understood, however, that it is not required for the non-lateral liquid migration material to overlap the non-woven fibrous material. Executions where it is the non-woven fibrous material which overlaps the non-lateral liquid migration material, and those where the two materials abut one another, while not necessarily preferred, are all within the scope of the present invention. It should also be understood that the manner or position of the materials in which one interface is joined need not be identical with the manner or position of the materials in which another is joined.
Finally, for ease of manufacture, it is preferred that such interface be generally linear, and such lines be generally perpendicular to the longitudinal centerline (and thus parallel to the transverse centerline) or to the transverse centerline (and thus parallel to the longitudinal centerline), as the case may be. It should be understood, however, that non-linear interfaces are also within the scope of the present invention.
Preferably, the article will have a pair of flexible flaps, one flap extending laterally from each longitudinal side of the main body thereof. Such flaps are capable of being folded about the crotch portion of the undergarment of the wearer. The flaps serve several purposes, including stabilizing the article within the garment of the wearer, and protecting the garment from being soiled by body exudate not absorbed and/or retained by the article. Such flaps comprise extensions of the thermoplastic film material of the intermediate zone of said cover layer of said main boldy, and typically comprise extensions of the barrier layer as well, bonded thereto. This construction, i.e. the cover layer of the flap being formed from the non-lateral liquid migration material (preferably an apertured thermoplastic film), prevents lateral wicking along the surface of the flap.
The absorbent system is below the cover layer. The absorbent system may comprise a single layer or a composite layer combining multiple layers or additional structures, the primary purpose of all of which is to absorb and retain exudate. Many different absorbent systems are known in the art. The absorbent system has two major surfaces, both of which are internal surfaces, i.e. they both face other layers of the napkin. The first surface faces the cover layer, the second surface faces the barrier layer.
Underneath the absorbent system is the barrier layer. The primary purpose of the barrier layer is to prevent exudate absorbed within the napkin from egressing the napkin on the opposite from which it was absorbed. The barrier layer is thus impervious to liquid but could be made pervious to gases to provide breathability. The barrier layer has two major surfaces, an external surface that faces the undergarment of the wearer when the napkin is in use, and an internal surface that faces the absorbent system.
Preferably, the cover layer and the barrier layer are joined to one another to form a flange seal around the periphery of the article to thus form an envelope or casing that fully encloses the absorbent system to provide a structurally integral napkin. It is preferred that this envelope surround, and thus contain, the absorbent system within it. Conventional methods of adhering or uniting the various components of the article together, such as adhesive between the components, are all within the scope of the present invention.
Other objects and features of the invention will become apparent by reference to the following description and the drawings.